4122 Background: BTCs are rare and aggressive malignancies. The first-line standard of care regimen for advanced BTC (aBTC) is gemcitabine (GEM), cisplatin, and an immune checkpoint inhibitor. Although FOLFOX is a preferred second-line treatment, it is limited by neuropathy. Nal-IRI contains IRI free base in liposome nanoparticles, which shelter IRI from conversion to its active metabolite (SN-38) and increase intratumoral SN-38 compared with IRI alone. The NAPOLI-1 trial of FU/LV/nal-IRI vs. FU/LV in second-line advanced pancreatic adenocarcinoma showed an overall survival (OS) benefit. The NIFTY trial (South Korea) demonstrated median OS (mOS) benefit of FU/LV/nal-IRI over FU/LV in a second-line aBTC population (8.6 vs. 5.3 months [mo], HR 0.68, 95% CI 0.48-0.95); however, the NALIRICC trial (Germany) did not (6.9 vs. 8.2 mo, HR 1.08, 95% CI 0.68-1.72). We sought to characterize second-line FU/LV/nal-IRI efficacy in US patients (pts) with second-line aBTC. Methods: This was a single-arm, open-label, multicenter phase II study of pts with aBTC previously treated with GEM/platinum chemotherapy. Pts received nal-IRI 70 mg/m 2 IV over 90 minutes, LV 400 mg/m 2 IV over 30 minutes every 14 days, and FU 2400 mg/m 2 IV over 46 hours every 14 days. The primary objective was to determine progression-free survival rate at 4 mo (PFS 4mo ) using RECIST v. 1.1 criteria. Median PFS reported for pts receiving second-line 5-FU doublet chemotherapy was 3 mo with a PFS of 30%. FU/LV/nal-IRI was of interest if it could increase the PFS 4mo to 50% or higher. Using a one-sided α of 0.05 and 80% power, 17 of 39 evaluable pts had to be progression-free at 4 mo to detect a difference in PFS 4mo between 30% and 50%. Results: Forty-eight pts were enrolled: median age 64.5 years; 69% women; 27% gallbladder primary; 54% intra- and 19% extrahepatic. Ten pts came off study due to toxicity without disease progression before 4 mo on study and were replaced to evaluate the PFS 4mo endpoint. Of 38 evaluable pts, 18 pts (PFS 4mo 47%) were alive and progression-free at 4 mo, meeting the primary endpoint. With a median follow-up of 7.1 mo, median time to disease progression or study discontinuation due to toxicity for all pts was 2.3 mo (95% CI 1.8-4.6, PFS 4mo 38%), and for pts evaluable for the primary endpoint, median PFS was 3.5 mo (95% CI 1.8-5.5). Five pts (10%) had PFS beyond 12 mo. mOS for all pts was 7.9 mo (95% CI 5.7-11.7). Of 41 evaluable pts, the response rate was 2% (1 PR), and the disease control rate was 54%. Adverse events (AEs) were consistent with known toxicities from the FU/LV/nal-IRI regimen. Conclusions: FU/LV/nal-IRI is an effective second-line regimen for aBTC in US pts. There was significant early toxicity as 21% of pts came off study due to AEs before 4 mo. Correlative studies, including longitudinal analyses of circulating tumor DNA using banked blood specimens, are planned (NCT04005339). Clinical trial information: NCT04005339 .

4522 Background: The relevance of ctDNA burden and longitudinal kinetics in RCC remains poorly defined. We applied AI–based analysis of quantitative ctDNA trajectories to identify prognostically informative patterns beyond baseline detection. Methods: We analyzed patients with mccRCC undergoing longitudinal tumor-informed ctDNA testing (Signatera) during first-line immune checkpoint inhibitor–based therapy. Quantitative ctDNA burden in mean tumor molecules per milliliter (MTM/mL) was measured serially and aligned to treatment initiation, with radiographic response classified as complete response (CR), partial response (PR), stable disease (SD), or progressive disease (PD). ctDNA trajectory similarity was independently assessed using dynamic time warping (DTW), trajectory-based K-means clustering, and a neural network sequence autoencoder (TensorFlow) with clustering to learn latent representations of ctDNA kinetics. Cross-method concordance was used to define robust ctDNA kinetic phenotypes. Results: Survival and response analyses included 93 patients with mccRCC with longitudinal ctDNA profiling. Baseline ctDNA detectability was not significantly associated with OS. Conversion from ctDNA-positive to ctDNA-negative status during therapy was associated with improved OS (p<0.05). Patients with radiographic disease control (CR/PR/SD) had significantly lower peak ctDNA levels than those with progressive disease (median 0.18 vs 8.86 MTM/mL; p=0.007). Increasing peak ctDNA burden was strongly associated with inferior OS (HR 2.21, 95% CI 1.63–3.01; p<0.001). A machine learning–based spline-regularized Cox survival model identified a high-risk ctDNA threshold >20 MTM/mL associated with worse OS (p=0.034). Trajectory-based K-means identified an optimal solution at k=4 clusters, independently supported by DTW and autoencoder-based analyses. Four ctDNA kinetic phenotypes repeatedly emerged: early ctDNA clearance, early ctDNA rise, delayed ctDNA clearance, and persistently low-level ctDNA. Autoencoder-derived phenotypes demonstrated strong internal robustness (Adjusted Rand Index, ARI ≈ 0.80) and high concordance with DTW-based clustering. Phenotypes were associated with distinct radiographic response and survival patterns, with early ctDNA rise conferring the poorest OS (p=0.022). Conclusions: AI-driven modeling of quantitative ctDNA burden and longitudinal kinetics identifies biologically interpretable and reproducible prognostic phenotypes in RCC, capturing higher-order temporal features of ctDNA dynamics and providing prognostic stratification beyond baseline detectability and burden alone, thereby informing clinical decision-making regarding earlier therapy switching.

Abstract Introduction: Circulating tumor DNA (ctDNA) enables minimally invasive monitoring of tumor biology and treatment response. Although ctDNA is increasingly used across malignancies, its utility in renal cell carcinoma (RCC) has not been well established. We sought to understand the relationship between ctDNA, tumor histology, and clinical outcomes in locally advanced (laRCC) and metastatic RCC (mRCC). Methods: Forty-eight patients with laRCC and mRCC underwent serial plasma ctDNA testing with a commercially available, tumor-informed assay (Signatera). Tissue from each patient’s tumor was sequenced to identify individualized variants, which were then used to construct a personalized tumor-informed ctDNA assay. Serial plasma testing quantified these patient-specific variants to assess ctDNA dynamics alongside interval imaging. Associations between baseline ctDNA status, peak level of ctDNA in mean tumor molecules per milliliter (MTM/mL), histologic subtype, aggressive morphologic features (sarcomatoid, rhabdoid, necrosis), and radiologic findings were analyzed. Quantitative variables were compared using Kruskal-Wallis and Mann-Whitney U tests. Survival was evaluated using Kaplan-Meier and log-rank testing. Results: ctDNA was detected at baseline in 39.5% (17/48) of patients overall, including 5.2% (1/19) with laRCC and 55.2% (16/29) with mRCC. Among clear cell (cc) RCC, baseline ctDNA was detected in 66% of cases with aggressive morphologic features (sarcomatoid, rhabdoid, or necrosis) versus 15% of clear cell tumors without these features. Baseline detection in non-clear cell RCC was 42% (3/7). Among ccRCC, the median peak ctDNA level was significantly higher in tumors with aggressive features compared to those without (0.82 vs 0.07 MTM/mL, p < 0.05). Peak ctDNA levels were strongly associated with radiologic disease status: patients with progressive disease (PD) had markedly higher median ctDNA levels (8.86 MTM/mL) compared with those demonstrating disease control with complete response (CR, 0.00 MTM/mL), partial response (PR, 0.41 MTM/mL), or stable disease (SD, 0.27 MTM/mL; H = 9.16, p = 0.027). When stratified by disease control (CR/PR/SD) versus disease progression (PD), patients with disease control exhibited significantly lower peak ctDNA levels (median 0.18 MTM/mL, n = 12) than those with progression (median 8.86 MTM/mL, n = 8; p = 0.007). Conversion from ctDNA-positive to ctDNA-negative during the disease course was associated with improved overall survival (p < 0.05). However, baseline ctDNA detection alone did not correlate significantly with survival. Conclusions: ctDNA may serve as a predictor of aggressive histopathologic features in RCC. Quantitative burden and ctDNA dynamics appear associated with disease status and overall survival. These findings highlight tumor-informed ctDNA as a promising biomarker in RCC. Citation Format: Eric Martin, Eun-mi Yu, Annika Murthi, Hongkun Wang, Laura Linville, Jeanny B. Aragon-Ching. Tumor-informed circulating tumor DNA dynamics reflect aggressive histology and radiologic disease status in renal cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 2583.

Abstract Background: PARP inhibitors (PARPi) induce synthetic lethality in BRCA1/2-mutant (BRCA-MUT) tumors and can activate DNA-damage-linked immune pathways. The TALAVE study (NCT03964532) examined the combination of the PARPi (talazoparib) with PD-L1 blockade (avelumab). Here we evaluated spatially resolved immune signaling and remodeling in response to talazoparib alone and with avelumab. Methods: 24 patients with advanced HER2-negative breast cancer (12 BRCA-MUT, 12 BRCA-WT) received talazoparib then talazoparib + avelumab. Serial biopsies (baseline, post-PARPi [BX2], post-combination [BX3]) underwent transcriptomic, spatial protein, and multiplex IF. BRCA-dependent TME remodeling and cellular neighborhood (CN) shifts were assessed. Results: BRCA-MUT tumors showed 83% objective response and 100% clinical benefit, whereas BRCA-WT tumors exhibited minimal activity. BRCA-MUT tumors became fragmented with increased immune activity, while BRCA-WT tumors remained compact and immunosuppressed. γH2AX and pTBK1 were spatially co-expressed and sustained in BRCA-MUT tumors during treatment but declined in BRCA-WT tumors. BRCA-MUT tumors displayed enrichment of CD8+ T cells and CD163+ macrophages after PARPi, whereas CD4+ T cells and CD68+CD163+ macrophages were depleted in BRCA-WT tumors. PD-1+ CD8+ T cells were strongly linked to local CD4+ T cell density, and PD-1+ frequency in CD8+ T cells correlated with longer PFS at baseline and BX3 in BRCA-MUT but not BRCA-WT tumors.CN analysis revealed CD4+ and CD8+ enriched neighborhoods with intermediate PD-1 expression that expanded after therapy in BRCA-MUT but not BRCA-WT tumors, and these CNs lacked PD-L1+ cells. Between BX2 and BX3, BRCA-MUT tumors sustained immune activity but showed no further T cell activation or infiltration. Spatial mapping identified three PD-L1+ CN types: (1) T cell-dense niches with high PD-1/PD-L1 and γH2AX-pTBK1 activity enriched only at baseline, largely lost after PARPi; (2) macrophage-T cell mixtures that were depleted during therapy; and (3) PD-L1+ dying tumor cells lacking pTBK1 activity and T cell engagement. Across contexts, PD-L1 was either lost before PD-L1 blockade or confined to regions isolated from T cells, leaving little opportunity to reinvigorate T cells. Conclusions: PARP inhibition reshaped the TME of BRCA-MUT tumors by inducing tumor fragmentation, sustaining γH2AX-pTBK1 signaling, and restoring CD4+ and CD163+ immune cells, whereas BRCA-WT tumors remained structurally intact and immunosuppressed. PD-1+ T cells localized to PD-L1-negative neighborhoods, and PD-L1+ tumor/myeloid cells were rapidly lost or confined to dying, immune-excluded regions, limiting the impact of PD-L1 blockade. Although PARPi re-engaged T cell programs in BRCA-MUT tumors, strategies beyond PD-L1 inhibition will be required to further enhance T cell infiltration and activation. Citation Format: Kenichi Shimada, Filipa Lynce, Claudine Isaacs, Xue Geng, Edward T. Richardson, Candace Mainor, Mei Wei, Julie M. Collins, Paula R. Pohlmann, Arielle L. Heeke, Kelly F. Zheng, Madeline Townsend, Lauren M. Sloat, Jane Staunton, Stuart J. Schnitt, Hongkun Wang, Joan S. Brugge, Geoffrey I. Shapiro, Jennifer L. Guerriero. Spatially resolved multi-omic profiling reveals BRCA-dependent immune remodeling during PARP inhibition and PD-L1 blockade [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3434.

BACKGROUND:Extreme long-distance running can produce recurrent gastrointestinal stress, including splanchnic hypoperfusion, mucosal injury, and post-exercise rectal bleeding, but its relationship to colorectal neoplasia is unclear. We therefore prospectively estimated the prevalence of advanced adenomas in endurance runners aged 35-50 years. This prevalence estimate is hypothesis-generating. METHODS:In this prospective, single-center, single-arm prevalence (cross-sectional) study (NCT05419531), participants had completed at least 2 ultramarathons (50 km or longer) or at least 5 marathons and had no colonoscopy within 10 years; key exclusions were inflammatory bowel disease, familial adenomatous polyposis, or Lynch syndrome. Participants completed a questionnaire and underwent colonoscopy. Advanced adenomas were defined as lesions 10 mm or larger, villous or tubulovillous histology (or > 25% villous component), or high-grade dysplasia. Prevalence was compared with a 1.2% historical rate reported in asymptomatic, average-risk adults aged 40-49 undergoing screening colonoscopy. RESULTS:Participants were recruited and consented from November 2022 to November 2024, and 94 participants (54.3% female; median age, 42 years) underwent colonoscopy between December 2022 and January 2025. Adenomas were found in 39 participants (41.5%), and advanced adenomas in 14 (15.0%; 95% binomial CI, 8.4-23.7%); no cancers were detected. Most advanced lesions were right-sided. The average number of adenomas per participant with non-advanced adenomatous polyps was 1.8. The average number of adenomas found amongst the participants with advanced adenomas was slightly higher at 2.2. CONCLUSIONS:In this endurance-runner sample, advanced adenomas were observed at a prevalence of 15.0% overall. Compared with historical screening benchmarks, prevalence appeared higher, supporting further evaluation of colorectal neoplasia risk in endurance runners. However, differences in symptom profile and other risk factors between this study population and historical screening populations limit direct comparability, and the findings should be considered hypothesis-generating. Larger controlled studies and mechanistic work are needed. TRIAL REGISTRATION:ClinicalTrials.gov NCT05419531.

BACKGROUND:ctDNA may refine risk stratification and treatment monitoring in urothelial carcinoma, but real‑world data integrating tumor‑informed assays across disease settings remain limited. We evaluated the prognostic and monitoring utility of ctDNA in locally advanced (laUC) and metastatic urothelial carcinoma (mUC). PATIENTS AND METHODS:We retrospectively reviewed adults with laUC or mUC who underwent tumor‑informed ctDNA testing at a single center. Relationship between baseline ctDNA status (positive/negative) and serial kinetics with TTrP, radiographic progression‑free survival (rPFS), and overall survival (OS) were assessed using Log‑rank tests and Cox Proportional Hazards models. RESULTS:Forty‑seven patients were included (laUC n = 24; mUC n = 23). Baseline ctDNA was detected in 16.6% of laUC and 60.8% of mUC. Median TTrP was 189 days for baseline ctDNA‑positive versus 553 days for ctDNA‑negative patients; in mUC, baseline ctDNA positivity was associated with shorter TTrP (Log‑rank P = .037). Absolute baseline ctDNA quantity was not associated with radiographic progression‑free survival (rPFS) (HR 1.007; P = .0518) or TTrP (HR 1.004; P = .2718). Median OS was 266 days for baseline ctDNA‑positive patients, while median OS was not reached for those with baseline ctDNA‑negative. On‑treatment decline and conversion from positive to negative were associated with improved outcomes; persistent positivity aligned with higher mortality (70% in baseline ctDNA‑positive mUC during follow‑up). CONCLUSIONS:In this single‑center cohort, ctDNA status and on‑treatment clearance were stronger indicators of prognosis than quantitative level. Baseline positivity identified patients at increased risk of earlier progression and death, and serial kinetics provided actionable early signals in routine practice. This data supports ctDNA‑informed management across laUC and mUC.

9591 Background: Circulating tumor DNA (ctDNA) has emerged as a sensitive biomarker for disease monitoring and prognostication across malignancies. Yet, the clinical relevance of sustained ctDNA negativity (“clearance”) as a guide for immunotherapy duration in advanced cutaneous cancers remains poorly defined. This study evaluated the prognostic impact of durable ctDNA clearance in patients with unresectable or metastatic skin cancers treated with immune checkpoint inhibitors (ICIs). Methods: A single-institution retrospective study was performed using a personalized ctDNA assay (Signatera, Natera Inc.) on prospectively collected plasma from patients with stage III–IV unresectable cutaneous malignancies receiving ICIs every 3-6 weeks. ctDNA clearance was defined as a change from ctDNA-positive to ctDNA-negative on at least two consecutive samples obtained ≥4 weeks apart during ICI therapy and categorized as transient (<12 months) or sustained (≥12 months). Demographics and clinical characteristics were summarized with descriptive statistics; progression-free survival (PFS) was estimated using the Kaplan-Meier method, and hazard ratios (HRs) were calculated with Cox proportional hazards models. Results: Among 75 patients (stage III: 23%, stage IV: 77%), most were male (72%) and had melanoma (87%), with a median age of 72 years and median follow-up of 20.4 months. Median ICI treatment duration was 6.9 months; all patients received ICIs, most commonly relatlimab/nivolumab (49%) or pembrolizumab (40%). Median ctDNA clearance duration was 8.2 months. Patients with sustained ctDNA clearance (n=25) experienced markedly improved 12-month PFS compared with those with transient clearance (n=50) (92.0% [95% CI, 71.6–97.9] vs 58.1% [95% CI, 42.6–70.8]). In a multivariable model adjusting for age, malignancy type, and treatment regimen, transient ctDNA clearance was associated with significantly worse PFS than sustained clearance (HR 12.1; 95% CI, 2.7-53.4). Conclusions: Sustained ctDNA clearance (≥12 months) is strongly associated with superior PFS in advanced cutaneous malignancies treated with ICIs, underscoring its potential as a dynamic biomarker to inform the treatment duration. Validation in larger, multi-institutional cohorts is warranted to confirm these findings and refine cDNA-guided immunotherapy strategies.

696 Background: ctDNA is a powerful tool that can detect MRD with limited but emerging data in patients (pts) with PDAC. We describe the clinical outcomes of pts with PDAC who underwent real-world MRD testing at our institutions. Methods: We retrospectively analyzed pts at 2 institutions with ≥1 tumor-informed ctDNA test (Natera, Inc) ordered for MRD testing post-operation (post-op) between June 2020-August 2024. Descriptive statistics were used to characterize clinicopathologic factors, ctDNA positivity (ctDNA+), and relapse rates (RR). Median relapse-free survival (mRFS) and overall survival (mOS) were calculated using Kaplan-Meier methods, comparisons between groups by log-rank test, and hazard ratios (HR) by Cox proportional hazard models. Associations between clinicopathologic factors and outcomes were assessed by Fisher’s exact and Chi-square tests. Results: Of the 54 pts who underwent MRD testing, 48 pts (88.9%) had successful tests. Failures were due to insufficient tissue. Patients with successful tests were staged as follows: 31.2% stage 1, 50.0% stage 2, and 18.8% stage 3, with 12.5% having R1/2 resections and 46.8% being node-positive. With a median follow-up of 21.0 months (mo), 22 (45.8%) pts had relapsed and 22 (45.8%) were anytime-ctDNA+. Sensitivity and specificity of ctDNA for relapse was 77.3% and 86.4%, respectively. Between anytime- and never-ctDNA+ pts, RR were 77.0% vs. 23.1%, mRFS 14.2 mo vs. not reached (NR) (HR 4.9, 95% CI 1.9-12.9), and mOS 31.7 mo vs. NR (HR 3.3, 95% CI 1.0-10.9), respectively. For 27 pts tested in the MRD window (2-12 weeks post-op), mRFS was 6.6 vs. 25.0 mo (HR 3.1, 95% CI 1.0-9.4) and mOS was 25.5 mo vs. NR (HR 2.5, 95% CI 0.6-10.2) in ctDNA+ vs. negative pts. ctDNA+ preceded radiographic relapse in 54.5% of patients with a median lead time of 166 days (IQR 70-332). In anytime-ctDNA+ pts, there were non-statistically significant trends for improved RFS and OS based on ctDNA decrease and clearance (table). No clinicopathologic factors predicted ctDNA+. Post-op ctDNA+ (p <0.001) and CA 19-9 (p=0.03) were the only factors that had a significant association with RFS. Conclusions: Post-op ctDNA is a strong prognostic marker for survival in PDAC, predicting relapse about five months before imaging. ctDNA+ status is independent of clinicopathologic factors and the strongest predictor of recurrence. These findings highlight a window where novel therapies could be tested to eradicate MRD. Longer follow up and prospective studies are needed to validate its predictive role with therapies in the MRD setting to improve outcomes in high-risk pts. RFS events/total mRFS (mo) HR (95% CI) p OS events/total mOS (mo) HR (95% CI) p ctDNA clearance Yes 6/9 17.0 0.61 (0.2-1.7) 0.35 2/9 NR 0.37 (0.08-1.8) 0.20 No 11/13 10.3 8/13 31.7 ctDNA MTM/mL reduction ≥50% 8/11 15.5 0.93 (0.3-2.9) 0.90 3/11 NR 0.54 (0.1-2.4) 0.42 <50% 6/8 13.6 4/8 31.7

e17138 Background: Active surveillance (AS) is one of the standard approach recommended for most prostate cancer men with low-risk prostate cancer. We examine the incidence of diagnosis, patterns of utilization of no treatment/active surveillance (AS) versus active treatment (Tx), clinical characteristics and trends of stage IV prostate cancer diagnosis in the United States using a hospital-based database. Methods: The National Cancer Database (NCDB) was queried with data including years 2010 – 2021. Demographics including race, and facility type, insurance, income type, Charlson-Deyo score (CDS) comorbidities, Staging, Gleason score, PSA, and treatment, AS were obtained. Trends and survival analyses were calculated. Results: There were 1137698 White (W) men, 220056 Black (B) men, and 69928 Hispanic (H) in the cohort. Median age for men on AS and treatment (Tx) was 66 y/o, median PSA was 6.4 ng/ml (AS) vs 7.8 ng/ml (Tx); AS was given in 149,340 W and 30,682 B and 10,062 H. AS occurred more in academic/research programs (44.6%) while Tx was given in 37.7%. There were significant difference in the rates of AS compared to Tx regarding median income and urban setting (p<.0001), and there were increased use of AS for stage I and II cancers (55.4% and 28.6% compared to those who had Tx 14.8% and 52.1% respectively), Gleason 3+3=6 (AS=32.2% vs 4.6% Tx), and PSA > 4 to < 10 ng/ml AS=70.6% vs Tx=57.2%. There were increasing trends of AS with recent years of diagnosis (AS rates of 13% vs T in 9.1% in 2021). For those who undergo Tx, Surgery occurred at 58.4% and was more common than radiation at 37%. Hormone therapy was recorded at 29.7%. Overall survival (OS) hazard ratio (HR) was 0.957 (0.925, 0.99; p=0.0117) after Inverse Probability Weighting (IPW) between AS vs Tx, Gleason score 6 vs >/=8 OS HR=0.206 (CI: 0.197,0.215; p <0.001) and treatment with radiation vs surgery OS HR=1.842 (CI: 1.686,2.011; p=<0.001). Overall, 149,172 men had stage IV prostate cancer diagnosis from 2010 to 2021, the incidence of stage IV disease numerically increased over time over the years from 6,832 patients in 2010 to 17,487 patients in 2021. Conclusions: Our analyses showed increasing trends of utilization of AS in prostate cancer patients with lower PSA, low Gleason score, academic/research settings, and urban settings, which are mostly guideline-concordant. Surgery was the most common modality for those who undergo treatment. There was an increasing incidence of stage IV diagnosis over time as well. Understanding these trends will help guide clinicians in appropriate adoption of active surveillance in practice settings.

143 Background: Molecular Tumor Boards (MTB) encompass a multidisciplinary approach to applying the latest advances in molecular oncology to patient care. The Inova Schar Cancer Institute (ISCI) MTB meets weekly to review every patient’s next generation sequencing (NGS) results and make recommendations for clinical trial options whenever applicable. Methods: We conducted a retrospective chart review of patients reviewed by the ISCI MTB to investigate correlations between patient demographics and MTB-recommended clinical trial (CT) participation. Chi square analysis was performed, with hypotheses tested at a 5% significance level. Results: The ISCI MTB reviewed NGS reports from 4,732 patients between January 2016 and December 2024, 635 (13.4%) of whom subsequently enrolled in a therapeutic clinical trial and received at least one dose of study drug. Of 2,806 Caucasian patients, 416 (14.8%) enrolled in a clinical trial compared to 219 of 1,926 (11.4%) non-Black/African American patients experienced a CT enrollment rate of 8.4% (51/604), significantly lower than that of Caucasian patients (p<0.0001). In an analysis of language preferences recorded in the electronic medical record (EMR), 14.2% (574/4,026) of patients who preferred English and 10.3% (61/592) of patients who preferred a language other than English enrolled in a clinical trial. Conclusions: Approximately 13% of patients reviewed by the ISCI MTB enrolled in an interventional clinical trial. Non-Caucasian patients and those for whom English was not a preferred language were less likely to participate in a clinical trial. Clinical trial enrollment in an MTB patient population by diagnosis, race, and preferred language. ISCI MTB Clinical Trial Enrollment Diagnosis Race Preferred Language in EMR Breast 16.0% (68/425) American Indian or Alaska Native 9.1% (1/11)r English 14.3% (574/4,026) CNS 17.2% (34/198) Another race 13% (36/277) Non-English 8.6% (61/706) GI 14.6% (258/1,763) Asian (All) 12.7% (87/685) GU 11.6% (50/431) Black/African American 8.4% (51/604) GYN 13.5% (58/427) Hispanic/Latino 10.6% (17/161) Head and Neck 10.3% (14/136) Middle Eastern 19.4% (6/31) Lung 9.5% (76/798) Native Hawaiian or Other Pacific Islander 11.1% (1/9) Skin 16.3% (53/326) Other 21.4% (6/28) Thoracic 9.1% (3/33) White/Caucasian 14.8% (416/ 2,806) Other * 10.8% (21/195) More than one race 4.3% (1/23) Unavailable/unknown 14.6% (13/89) *Other consists of hematology, sarcoma, other, multiple primary and unknown malignancies.

BACKGROUND:One in five adults aged 40 will develop heart failure (HF) during their lifetime. Risk factors (e.g., hypertension, diabetes mellitus, coronary artery disease, etc.) lead to structural and functional changes in cardiomyocytes, resulting in HF. At the cellular level, these changes consist of mis/over-expression of genes that regulate cardiac identity (e.g., CamK2δ, PKC, Stat3, etc.). The current paradigm for treating HF is pharmacological or device-based intervention; however, with few exceptions, the condition worsens with time. We are proposing to implement a change in HF treatment, shifting from a drug-centric system to a cardiac target-specific molecular approach that would reverse hypertrophy and adverse remodelling of affected cardiomyocytes. METHODS:A cardiomyocyte targeting peptide (CTP) was reversibly linked to miRNA106a for delivery to a mouse model of HF. Reversal of morphological, signalling, and physiological HF parameters was measured. Additionally, CTP-miRNA106a was introduced into a human cardiomyocyte cell line to identify mechanism(s) at play for reversing HF characteristics (e.g., hypertrophy). RESULTS:Bio-distribution studies showed that intravenously injected CTP-miRNA106 delivered its cargo specifically to the heart within 30 min, followed by clearance of CTP from the heart to the kidneys, and to a lesser extent, the liver by 35 h with persistence of miRNA106a in cardiomyocytes until day 7 (the latest tested time-point). CTP-miRNA106a reversed angiotensin2/isoproterenol-induced hypertrophy in 90% of the treated mice. We also identified two potential HF intracellular signalling pathways/mechanisms (PLCβ1/PKC/IP3 and NF-κB) targeted by CTP-miRNA106a that could benefit many pathophysiologies underlying HF, including inflammation. CONCLUSIONS:CTP-miRNA106a, a first-of-a-kind cardiac-specific drug, downregulates genes involved in cardiac hypertrophy and inflammation through the PLCβ1 and CamKIIδ kinase pathways. CTP delivery of miRNA106a cargo is specific to cardiomyocytes both in vitro and in vivo, and once delivered, many HF parameters, including hypertrophy, are reversed. KEY POINTS:Cardiac Targeting Peptide (CTP) delivers, specifically to the heart, reversibly linked miRNA106a. MiRNA106a targets genes in various pathways known to cause heart failure when they are over/hyper activated returning their expression to normal levels. In vivo analyses using a mouse heart failure model resulted in reversal of heart failure parameters in 19/20 mice.

623 Background: The EpiSwitch Checkpoint Inhibitor Response Test (CiRT) is a blood-based assay that analyzes DNA conformations in immune cells to predict responses to immune checkpoint inhibitors (ICIs) targeting PD-L1/PD-1. CiRT has demonstrated superior predictive accuracy compared to traditional biomarkers, such as tumor mutational burden (TMB) and PD-L1 immunohistochemistry (IHC), for predicting responses in urothelial cancer (ESMO 2022). However, its role in hepatocellular carcinoma (HCC) and other gastrointestinal (GI) tumors remains unclear. As immunotherapy becomes more common in these cancers, identifying reliable predictive biomarkers is essential to optimize treatment outcomes. Methods: This retrospective study evaluates CiRT-predicted immunotherapy responses and clinical outcomes in patients with HCC and GI tumors, including cholangiocarcinoma, pancreatic adenocarcinoma, and gastric cancer. All patients received one or more lines of immunotherapy. CiRT responses were categorized into high probability (HP) and low probability (LP). Treatment response was assessed per RECIST 1.1 criteria. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), overall survival (OS), and progression-free survival (PFS) were analyzed. Results: 43 patients (24 HP, 19 LP) were included. HCC patients (n = 33) received varied immunotherapy regimens, such as combinations of bevacizumab with atezolizumab, tremelimumab with durvalumab, and nivolumab with ipilimumab. Non-HCC patients (n = 10) received combinations of immunotherapy and chemotherapy such as durvalumab with cisplatin and gemcitabine and nivolumab with oxaliplatin and capecitabine. Across all patients, CiRT revealed a sensitivity of 73.91%, a specificity of 65%, a PPV of 70.83%, and an NPV of 68.42%. In HCC, sensitivity was 70.59% and specificity was 68.75%. In non-HCC, sensitivity was 83.33% and specificity 50%. HP responders showed better treatment outcomes compared to LP responders, with higher rates of complete response (CR: 12.5% vs 0%), partial response (PR: 29.2% vs 21.1%), and stable disease (SD: 29.2% vs 10.5%), and a lower rate of progressive disease (PD: 29.2% vs 68.4%) (p = 0.0467). Overall, 70.83% of HP achieved CR, PR, or SD vs. 31.58% of LP (p = 0.0098). PFS was significantly better in HP (p = 0.044, Log-rank test; median PFS = 2.0 months for the LP group, mPFS not reached for the HP group). No statistically significant OS difference was noted due to the lack of events in the HP group. Conclusions: CiRT HP status was associated with improved response rates to immunotherapy, longer PFS, and better treatment outcomes in HCC and GI tumors. HP responders experienced notably better outcomes, suggesting that CiRT could serve as a promising predictive biomarker for immunotherapy response, addressing a critical unmet need for reliable biomarkers to treat HCC and other GI tumors.

11150 Background: The role of palliative chemotherapy (PC) in patients with advanced solid tumors and poor performance status (PS) remains uncertain since this population is underrepresented in clinical trials. Retrospective studies of patients with an Eastern Cooperative Oncology Group-Performance Status (ECOG-PS) > 2 consistently demonstrate poorer survival and increased treatment-related toxicities. This study aimed to evaluate the clinical impact of PC in hospitalized patients and its association with PS and outcomes. Methods: This retrospective chart review was conducted between January 2018 and July 2024 across a five-hospital health system. The primary endpoint was overall survival (OS), defined as the time from the first dose of inpatient chemotherapy to death or last follow-up. Secondary outcomes included in-hospital mortality, length of stay, 30- and 60-day mortality, and toxicity. Continuous variables were compared using the Mann-Whitney U test or the two-sample t-test and categorical variables were compared using the Chi-squared or Fisher’s exact test. Time to event data were assessed using the Kaplan-Meier method. A p-value < 0.05 was considered statistically significant. Results: A total of 383 patients were included in this study. Of these, 227 patients had an ECOG-PS ≤ 2, and 156 patients had an ECOG-PS > 2. The median age was 60 years, and 57% were female. Common primary tumor sites included gastrointestinal, gynecologic, and lung. At presentation, 288 patients were chemotherapy-naïve, and 88% were hypoalbuminemic. The median OS was 188 days. Patients with an ECOG-PS ≤ 2 had a significantly longer median OS compared to those with an ECOG-PS > 2 (293 vs 77 days, p<0.0001). Mortality rates were higher in patients with ECOG-PS > 2 during the index hospitalization (17% vs 6%, p=0.0005), at 30 days (24% vs 14%, p=0.015), and at 60 days (36% vs 21%, p=0.001). Despite these differences, bleeding and infection rates were similar between groups. Median duration of hospitalization was 13 days, with significantly longer stays observed in patients with poor PS (16 vs 10 days, p<0.0001). Although toxicity rates were comparable overall, patients with ECOG-PS > 2 experienced significantly higher rates of thrombocytopenia (39% vs 25%, p=0.018) and neutropenia (40% vs 27%, p=0.028). In univariate analysis, significant predictors of shorter survival included ECOG-PS > 2 (p<0.0001), age > 60 (p=0.0097), Charlson Comorbidity Index ≥ 8 (p=0.02), hypercalcemia (p=0.0014), and hypoalbuminemia (p=0.0014). In multivariate analysis, all factors except age > 60 remained independent predictors of shorter survival. Conclusions: PC in hospitalized cancer patients with ECOG-PS > 2 was associated with shorter survival, longer hospital stays, and higher rates of early mortality. These findings emphasize the importance of careful patient selection and the need for further research to optimize care strategies in this population.

Ewing sarcoma (ES) is a pediatric malignancy that lacks adequate therapies for its metastatic form. These tumors constitutively express neuropeptide Y (NPY) and its Y5 receptor (Y5R), which leads to elevated levels of the peptide in patients' serum. In animal models, xenografts secreting NPY metastasize to extrapulmonary niches, including bone; the phenotype associated with adverse prognosis in ES patients. To determine the role of the NPY/Y5R axis in ES extrapulmonary dissemination, we used a doxycycline-inducible CRISPR/Cas9 system to knockout Y5R in SK-ES-1 xenografts that metastasize to these niches. We have shown that metastases developing from heterogenous SK-ES-1/Y5R-sgRNA primary tumors in doxycycline-treated mice were initiated exclusively by SK-ES-1 clones with a functional NPY5R gene. Similarly, metastasis from wild type SK-ES-1 xenografts was associated with a selection of clones with NPY5R gene gain. In vitro assays identified Y5R-dependent ES cell motility driven by RhoA activation as the mechanism underlying the metastatic effects of NPY. In ES cell lines that secrete NPY, the autocrine NPY/Y5R loop was responsible for maintaining basal cell motility, while ES cells that do not release the peptide responded to the exogenous NPY. These data provide evidence for the crucial role of the NPY/Y5R axis in ES metastasis.

3619 Background: Exercise induced gastrointestinal injury is believed to be associated with reduced blood flow to the intestines during long distance running. To our knowledge, there has not been evidence linking this type of exercise- induced bowel ischemia to carcinogenesis. After observing multiple “ultramarathoners” present to our cancer center with advanced colorectal cancer, we initiated a prospective IRB-approved study to evaluate the risk of advanced adenomas (AA) in long distance runners between the ages of 35-50. Methods: NCT 05419531 was a prospective study of subjects aged 35-50 years who had completed at least two registered ultramarathons (50 km or longer) or five registered marathons (26.2 miles). Subjects were excluded if they were known or suspected to have inflammatory bowel disease, familial adenomatous polyposis (FAP), or Lynch Syndrome. Prior to colonoscopy, each subject completed a questionnaire regarding dietary habits, bowel habits, and long-distance running history, with results to be reported in the future. All polyps discovered during colonoscopy were reviewed by a panel of gastroenterologists, pathologists, and oncologists to determine if they met the criteria for advanced adenomas, defined as lesions >10 mm, >25% tubulovillous features, or high-grade dysplasia. Results: Between October 2022 and December 2024, 102 subjects were screened, and 100 underwent colonoscopy as part of the study. The median age was 42.5 years; 55 of the participants were female and 45 were male. The historical benchmark used for expected AAs in average-risk individuals aged 40-49 years was 1.2%. Among the 100 subjects in this study, 15% (95% exact confidence interval: 7.9%- 22.4%) had confirmed AAs. 39 out of 100 subjects had at least one adenoma. Three additional subjects had three or more adenomas but did not meet our predefined criteria for AA and were not included among the 15 patients with AA. Conclusions: NCT 05419531 achieved its predefined endpoint for advanced adenomas, suggesting that “intensive” long distance running is a risk factor for advanced adenomas of the colon. Consideration of refined screening strategies for this population is warranted. Future pathological and epidemiological evaluations should explore causation and ancillary risk factors in this unique population. Clinical trial information: NCT05419531 . Subjects with advanced adenoma. Participant ID 3 9 15 16 37 53 55 67 69 71 77 87 91 98 100 Gender F M M F F M F F F F F M M F M Age 44 45 48 41 45 49 40 40 45 39 42 50 42 44 41 Endurance Eligibility (U – Ultramarathons; M – Marathons) 4 - 6 U 4 - 6 U > 15 U 4 - 6 U > 15 U 7 - 15 U 6 M 5 M 7 - 15 U 1 U / 7-8 M > 15 U > 15 U 10 M > 15 U 5 M # of Polyps 3 on primary; 2 on secondary 5 2 3 1 1 3 2 7 1 2 4 2 6 3 Size of largest polyp (Colonoscopy/Pathology) (mm) 25 / 15 12 / 15 10 / 13 10 / 10 3 / 3 20 / 9 5-6 / 5 12/11 12 / 12 5 / 5 5 / 5 15-20 / 12 6 / 7 10 / 7 10 / 19 >25% Tubulovillous Features (Y/N) N N N N Y N Y N N Y Y N N Y N High-grade Dysplasia (Y/N) N N N N N N N N N N N N Y N N

685 Background: The role of ctDNA is emerging as an adjunctive prognostic tool for survival in the laUC setting, but its role is evolving in mUC. We aimed to analyze ctDNA in the real-world setting and correlate its trend with available clinical, radiographic, and next generation sequencing (NGS) data. Methods: Patients with a diagnosis of laUC and mUC were included in the analysis of an IRB-approved protocol. Clinical/pathologic stage, systemic therapy received, NGS (TEMPUS) results, and tumor-informed detection and quantification (Signatera, Natera, Inc) was analyzed with baseline ctDNA data (positive + vs. negative -). Mean tumor molecules (MTM) levels were obtained and time to radiographic progression (TTrP), radiographic progression-free survival (rPFS) and overall survival (OS) evaluated. If baseline ctDNA was negative (ctDNA-), time to initial ctDNA+ was recorded. Analyses of time in days (d) from ctDNA- to ctDNA+ with regard to radiographic progression and OS was analyzed using Kaplan-Meier method and between group comparison by Log-rank test. Descriptive statistics were used to evaluate ctDNA trends in patients receiving various systemic therapies. Results: 47 patients (n=24 laUC; n=23 mUC) were included in analyses; 34 Male, 14 Female. The median rPFS in patients with baseline ctDNA+ was 189d. Higher baseline levels did not significantly affect rPFS (p=0.0518, HR=1.007) or TTrP (p=0.2718, HR=1.004). The median rPFS in baseline ctDNA- level was 553d. The overall TTrP was worse in mUC baseline ctDNA+ vs baseline ctDNA- (log-rank p=0.037). Median OS in baseline ctDNA+ was 266d and ctDNA- was not evaluable. Patients who received immunotherapy-based treatment or antibody-drug-conjugate based therapy had a decline in baseline ctDNA at 1 month follow up. Lack of response or clearance of ctDNA served as predictor of mortality. Of the mUC patients who had baseline ctDNA +, mortality was as high as 70% at the time of follow up. No correlation with specific NGS findings were seen. Conclusions: The use of ctDNA allowed for identification of earlier disease relapse than radiographic imaging alone which allows for earlier switch in therapeutic management. Obtaining a baseline positive ctDNA result without conversion to a negative value portends a poor prognosis in mUC.

Effective second-line treatment for advanced biliary tract cancer (BTC) remains an unmet need. BTC often presents with homologous recombination repair (HRR) pathway deficiencies and IDH1/IDH2 mutations which suggest responsiveness to Poly (ADP-ribose) polymerase inhibitors. Thirteen patients were enrolled in our open-label, single-site phase II study of pembrolizumab and olaparib in the second-line setting and beyond for patients with advanced BTC. The objective response rate was 15.4% and the disease control rate was 53.8%. The median progression-free survival (PFS) was 5.45 months (95% CI 1.25-7.82), and the median overall survival was 7.21 months (95% CI 4.5-13.8). Both patients with IDH1 mutations and 2 of the 4 patients with HRR mutations achieved a PFS of at least 7.5 months. All BTC patients do not appear to benefit from pembrolizumab plus olaparib, but those with HRR deficiencies and/or IDH mutations may benefit although it would now represent a rechallenge with immunotherapy. Trial registration: NCT04306367, date of registration 3/10/2020.

We were able to identify potential prognostic capability of the Computer Assisted Nodule Analysis and Risk Yield (CANARY) program in the determination of occult lymph node metastasis in clinical stage I-IIA lung adenocarcinoma. In a single-institution cohort of 228 patients, those with poor risk determined by Score Indicative of Lung Cancer Aggression (SILA) has a 3-fold increase in likelihood of having occult lymph node metastasis (odds ratios = 3.3 [1.6-9.2]). Background: Current staging work-up does not capture all occult lymph node (OLN) disease. We sought to determine if Computer Assisted Nodule Analysis and Risk Yield (CANARY) analysis could help distinguish OLN status in early-stage lung adenocarcinoma. Methods: Retrospective review of resected lung cancer patients from 2016 to 2021 was performed. Patients with surgically resected clinical stage I-IIA lung adenocarcinoma were included. Preoperative imaging was entered into the CANARY software, and each lesion was categorized into good, intermediate, and poor risk. OLN status was determined per pathology results. Pearson's Chi-square correlation, univariate and multivariate logistic regression models were used to assess OLN metastases as a function of CANARY risk profile, with statistical significance at alpha = 0.05. Results: In total, the study cohort included 228 patients with median age of 70. By clinical stage, 195 (85.5%), 24 (10.5%), and 9 (3.9%) patients were determined to be in IA, IB, and IIA, respectively. 28 (12.3%) patients were found to have OLN metastases. Among them, 1 (3.6%), 3 (10.7%), and 24 (85.7%) patients had a good, intermediate, and poor CANARY risk profile, respectively. CANARY risk profile was significantly associated with OLN metastases (chi 2 = 9.9, P = .007). Relative to the good/intermediate group, patients with poor risk had a more-than 3-fold increase in likelihood of having OLN metastases (odd ratio [OR] = 3.3, 95% confidence interval [CI]:1.6-9.2, P = .007). Conclusion: CANARY analysis was able to risk-stratify the likelihood of OLN metastases in early-stage lung adenocarcinoma. CANARY can provide an adjunctive non-invasive tool to aid in determining an appropriate individualized treatment plan.